5,548 research outputs found

    Extreme drought impacts have been underestimated in grasslands and shrublands globally

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    Climate change is increasing the frequency and severity of short-term (~1 y) drought events‚ÄĒthe most common duration of drought‚ÄĒglobally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function‚ÄĒaboveground net primary production (ANPP)‚ÄĒwas 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought

    <em>TESS</em> Cycle 2 observations of roAp stars with 2-min cadence data

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    \ua9 The Author(s) 2023.We present the results of a systematic search of the Transiting Exoplanet Survey Satellite (TESS) 2-min cadence data for new rapidly oscillating Ap (roAp) stars observed during the Cycle 2 phase of its mission. We find seven new roAp stars previously unreported as such and present the analysis of a further 25 roAp stars that are already known. Three of the new stars show multiperiodic pulsations, while all new members are rotationally variable stars, leading to almost 70 per cent (22) of the roAp stars presented being őĪ2 CVn-type variable stars. We show that targeted observations of known chemically peculiar stars are likely to overlook many new roAp stars, and demonstrate that multiepoch observations are necessary to see pulsational behaviour changes. We find a lack of roAp stars close to the blue edge of the theoretical roAp instability strip, and reaffirm that mode instability is observed more frequently with precise, space-based observations. In addition to the Cycle 2 observations, we analyse TESS data for all-known roAp stars. This amounts to 18 further roAp stars observed by TESS. Finally, we list six known roAp stars that TESS is yet to observe. We deduce that the incidence of roAp stars amongst the Ap star population is just 5.5 per cent, raising fundamental questions about the conditions required to excite pulsations in Ap stars. This work, coupled with our previous work on roAp stars in Cycle 1 observations, presents the most comprehensive, homogeneous study of the roAp stars in the TESS nominal mission, with a collection of 112 confirmed roAp stars in total

    Evaluation of birth by cesarean delivery and development of early-onset colorectal cancer

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    IMPORTANCE: The incidence of early-onset colorectal cancer (CRC), diagnosed younger than 50 years of age, has increased worldwide. Gut dysbiosis throughout the life course is hypothesized as a leading mechanism, yet epidemiologic data are limited. OBJECTIVE: To prospectively examine the association between birth by cesarean delivery and early-onset CRC among offspring. DESIGN, SETTING, AND PARTICIPANTS: In this population-based, nationwide case-control study in Sweden, adults diagnosed with CRC between 18 and 49 years of age from 1991 to 2017 were identified through the Epidemiology Strengthened by Histopathology Reports in Sweden (ESPRESSO) cohort. Up to 5 general population control individuals without CRC were matched with each case on age, sex, calendar year, and county of residence. Pathology-confirmed end points were linked with the Swedish Medical Birth Register and other national registers. Analyses were conducted from March 2022 through March 2023. EXPOSURE: Birth by cesarean delivery. MAIN OUTCOMES AND MEASURES: The primary outcome was development of early-onset CRC in the overall population and by sex. RESULTS: We identified 564 case patients with incident early-onset CRC (mean [SD] age, 32.9 [6.2] years; 284 [50.4%] male) and 2180 matched controls (mean [SD] age, 32.7 [6.3] years; 1104 [50.6%] male). Compared with vaginal delivery, birth by cesarean delivery was not associated with early-onset CRC in the overall population (adjusted odds ratio [aOR], 1.28; 95% CI, 0.91-1.79) after multivariable adjustment for matching and maternal and pregnancy-related factors. A positive association was found for females (aOR, 1.62; 95% CI, 1.01-2.60), but there was no association for males (aOR, 1.05; 95% CI, 0.64-1.72). CONCLUSIONS AND RELEVANCE: In this nationwide, population-based case-control study, birth by cesarean delivery was not associated with early-onset CRC compared with birth by vaginal delivery in the overall population in Sweden. However, females born by cesarean delivery had greater odds of early-onset CRC compared with individuals born through vaginal delivery. This finding suggests that early-life gut dysbiosis may contribute to early-onset CRC in females

    Design and Modeling of Modified Interleaved Phase-Shifted Semi-Bridgeless Boost Converter for EV Battery Charging Applications

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    Electric vehicles (EVs) are set to become one of the domestic transportation systems that are highly preferred over conventional vehicles. Due to the huge demand for and cost of fuel, many people are switching over to EVs. Companies such as Tesla, BMW, Audi, and Mercedes have started marketing EVs. These EVs need charging stations to charge the batteries. The challenges for EV batteries require the implementation of features such as fast charging, long-run utilization, reduced heat emission, a light weight, and a small size. However, fast charging using conventional converters generates an imbalance in current injection due to the passive component selection. In this study, a converter is proposed that uses an interleaved network that provides a balanced current injection; i.e., an improved interleaved phase-shifted semi-bridgeless boost converter (IIPSSBBC) is designed for EV battery charging applications. The suggested approach is mathematically designed using MATLAB/Simulink (2021) software. The result shows that the battery charging current achieves about 16.5 A, which is relatively more than conventional systems. Moreover, the charging time of the proposed converter is about 6 hrs for a 50 Ah battery with a discharge load capacity of 5000 W, which is relatively less than the conventional method. In a nutshell, compared with conventional converters, the IIPSSBBC performs better, and, notably, the charging speed and current injection are increased by two times the amount. Further, a prototype hardware model is developed to assess the performance of the proposed converter

    Evaluating the consistency between OCO-2 and OCO-3 XCO<sub>2</sub> estimates derived from the NASA ACOS version 10 retrieval algorithm

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    Abstract. The version¬†10 (v10) Atmospheric Carbon Observations from Space (ACOS) Level¬†2 full-physics (L2FP) retrieval algorithm has been applied to multiyear records of observations from NASA's Orbiting Carbon Observatory 2 and 3 sensors (OCO-2 and OCO-3, respectively) to provide estimates of the carbon dioxide (CO2) column-averaged dry-air mole fraction (XCO2). In this study, a number of improvements to the ACOS¬†v10 L2FP algorithm are described. The post-processing quality filtering and bias correction of the XCO2 estimates against multiple truth proxies are also discussed. The OCO¬†v10 data volumes and XCO2 estimates from the two sensors for the time period of August 2019 through February 2022 are compared, highlighting differences in spatiotemporal sampling but demonstrating broad agreement between the two sensors where they overlap in time and space. A number of evaluation sources applied to both sensors suggest they are broadly similar in data and error characteristics. Mean OCO-3 differences relative to collocated OCO-2 data are approximately 0.2 and ‚ąí0.3‚ÄČppm for land and ocean observations, respectively. Comparison of XCO2 estimates to collocated Total Carbon Column Observing Network (TCCON) measurements shows root mean squared errors (RMSEs) of approximately 0.8 and 0.9‚ÄČppm for OCO-2 and OCO-3, respectively. An evaluation against XCO2 fields derived from atmospheric inversion systems that assimilated only near-surface CO2 observations, i.e., did not assimilate satellite CO2 measurements, yielded RMSEs of 1.0 and 1.1‚ÄČppm for OCO-2 and OCO-3, respectively. Evaluation of uncertainties in XCO2 over small areas, as well as XCO2 biases across land‚Äďocean crossings, also indicates similar behavior in the error characteristics of both sensors. Taken together, these results demonstrate a broad consistency of OCO-2 and OCO-3 XCO2 measurements, suggesting they may be used together for scientific analyses

    Investigation on the effect of charge injection from non-thermal plasma on soot formation in laminar coflow diffusion flame

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    A novel, modified coflow burner was developed to study the effect of charge injection from a non-thermal plasma into three helium-diluted laminar coflow diffusion ethylene flames. The frequency of the high voltage (HV) signal was varied to control the ion concentration (charge) injected into the flames. Optical emission spectroscopy was used to characterize the non-thermal plasma while a bias plate methodology was used to gauge the relative amount of charge generated. For different HV signal frequencies, the laser-induced fluorescence of OH, chemiluminescence of CH*, and laser-induced incandescence of soot in flames were measured. The OH and CH* measurements showed that the flames retained the classic flame shape with charge injection. Significant soot reduction was observed at low HV signal frequencies, corresponding to an increase in charge injection. Notably, at low HV signal frequency, soot reduction in highly concentrated (60%) ethylene flame is three times lower than the less concentrated (32%) ethylene flame. This can be attributed to the decrease in the injected charge to soot precursor concentration ratio when the concentration of ethylene in the flame is increased. These results demonstrate that the current system is a promising candidate for studying the charge effect from non-thermal plasma on soot formation in laminar coflow diffusion flames.National Research Foundation (NRF)Published versionThis research was supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme. Y. R. Tan acknowledges financial support from Fitzwilliam College Cambridge, Trinity College Cambridge and the Cambridge Trust. M. Kraft gratefully acknowledges the support of the Alexander von Humboldt Foundation. M. Salamanca is grateful with Universidad Nacional de Colombia-Sede Medellín for its support

    TESS Cycle 2 observations of roAp stars with 2-min cadence data

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    We present the results of a systematic search of the Transiting Exoplanet Survey Satellite (TESS) 2-min cadence data for new rapidly oscillating Ap (roAp) stars observed during the Cycle 2 phase of its mission. We find seven new roAp stars previously unreported as such and present the analysis of a further 25 roAp stars that are already known. Three of the new stars show multiperiodic pulsations, while all new members are rotationally variable stars, leading to almost 70 per cent (22) of the roAp stars presented being őĪ2 CVn-type variable stars. We show that targeted observations of known chemically peculiar stars are likely to overlook many new roAp stars, and demonstrate that multi-epoch observations are necessary to see pulsational behaviour changes. We find a lack of roAp stars close to the blue edge of the theoretical roAp instability strip, and reaffirm that mode instability is observed more frequently with precise, space-based observations. In addition to the Cycle 2 observations, we analyse TESS data for all known roAp stars. This amounts to 18 further roAp stars observed by TESS. Finally, we list six known roAp stars that TESS is yet to observe. We deduce that the incidence of roAp stars amongst the Ap star population is just 5.5 per cent, raising fundamental questions about the conditions required to excite pulsations in Ap stars. This work, coupled with our previous work on roAp stars in Cycle 1 observations, presents the most comprehensive, homogeneous study of the roAp stars in the TESS nominal mission, with a collection of 112 confirmed roAp stars in total

    Interstellar Probe - To Touch Interstellar Space

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    International audienceAfter the exciting in-situ observations of the termination shock and the entry of the Voyager spacecraft into the inner and possibly outer heliosheath, there is a growing awareness of the significance of the physics of the outer heliosphere. Its understanding helps to clarify the structure of our immediate interstellar neighborhood, contributes to the clarification of fundamental astrophysical processes like the acceleration of charged particles at a stellar wind termination shock and beyond, and also sheds light on the question to what extent interstellar-terrestrial relations are important for the environment of and on the Earth and of exoplanets. In order to explore the boundary region of the heliosphere, it is necessary to send a spacecraft to perform advanced in-situ measurements particularly in the heliosheath, i.e. the region between the solar wind termination shock, and the heliopause, as well as in the (very) local interstellar medium. Solar activity is decreasing to 'normal values' below those of the Grand Solar Maximum which was typical of the space age so far. This is likely to reduce the size of the heliosphere and allows us to study a 'normal' heliosphere by launching an Interstellar Probe (IP) which will also provide within a shorter time than previously believed the first comprehensive measurements of key parameters of the local interstellar environment such as its composition, state, and magnetic field. Together with an accurate determination of the state of the heliospheric plasma across the heliosphere, these quantities are crucial to our understanding of how the heliosphere, and, much more generally, astrospheres, are formed and how they react to varying interstellar environments

    Process design, simulation, and techno-economic analysis of integrated production of furfural and glucose derived from palm oil empty fruit bunches

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    This study aims to propose a new process design, simulation, and techno-economic analysis of an integrated process plant that produces glucose and furfural from palm oil empty fruit bunches (EFB). In this work, an Aspen Plus-based simulation has been established to develop a process flow diagram of co-production of glucose and furfural along with the mass and energy balances. The plant‚Äôs economics are analyzed by calculating the fixed capital income (FCI), operating costs, and working capital. In contrast, profitability is determined using cumulative cash flow (CCF), net present value (NPV), and internal rate of return (IRR). The findings show that the production capacity of 10 kilotons per year (ktpy) of glucose and 4.96 ktpy of furfural with a purity of 98.21 and 99.54%‚ÄĒweight, respectively, was achieved in this study. The FCI is calculated as United States Dollar (USD) 20.80 million, while the working and operating expenses are calculated as USD 3.74 million and USD 16.93 million, respectively. This project achieves USD 7.65 million NPV with a positive IRR of 14.25% and a return on investment (ROI) of 22.06%. The present work successfully develops a profitable integrated process plant that is established with future upscaling parameters and key cost drivers. The findings provided in this work offer a platform and motivation for future research on integrated plants in the food, environment, and energy nexus with the co-location principle
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